JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="left-container">Autofill remaining width</div>
    <div class="fixed-container">200px</div>
</div>

CSS

.container{
  display: flex;
}
.left-container {
  background-color: red;
  flex: 1;
}
.fixed-container {
  flex-basis: 200px;
  background-color: yellow;
  text-align: center;
}